In our news wrap Friday, more than 170 countries signed the landmark Paris Agreement on climate change at the United Nations headquarters in New York. Also, the official death toll from last week’s earthquake in Ecuador climbed again, reaching 587. And as aid workers warn of delays in distributing supplies to the survivors, a new threat has emerged in the form of mosquito-borne illness.

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JUDY WOODRUFF:

Good evening. I'm Judy Woodruff.

On the "NewsHour" tonight: U.S. suicide rates climb to a 30-year high, especially among young girls. We examine this disturbing trend.

Also ahead, extending the right to vote in Virginia. An executive order restores voting rights to convicted felons.

Then, on this Earth Day: efforts by famed biologist and father of biodiversity E.O. Wilson to save Alabama's river delta.

E.O. WILSON, Biologist:

We have only discovered, much less studied, about 20 percent of all the species. So, here is a world that is waiting for exploration, and that's just the beginning.

JUDY WOODRUFF:

And it's Friday. Mark Shields and David Brooks are here to analyze the week's news.

All that and more on tonight's "PBS NewsHour."

(BREAK)

JUDY WOODRUFF:

It took all day, but more than 170 countries signed the landmark Paris accord on climate change today. The ceremony took place at the United Nations in New York. Secretary of State John Kerry signed for the United States, with his granddaughter joining him.

Beforehand, he acknowledged the deal falls short of its stated goal.

JOHN KERRY, Secretary of State: The power of this agreement is not that it, in and of itself, guarantees that we will actually hold the increase of temperature to the target of 1.5 degrees or 2 degrees Centigrade. In fact, it doesn't. And we know that. We acknowledge it. The power of this agreement is the opportunity that it creates.

JUDY WOODRUFF:

Each nation will set nonbinding targets for cutting emissions of carbon dioxide and other gases by 2025. The U.S. target is up to 28 percent below 2005 levels.

A new earthquake hit off the coast of Ecuador last night, followed by a smaller aftershock, but there were no reports of new damage. Still, the official death toll from last Saturday's quake rose again to 587. Survivors are now lining up daily for food and fresh water, as aid workers warn of delays in distributing the supplies. And a new risk has emerged, the threat of mosquito-borne illness.

The U.S. presidential candidates are heading into another big weekend, the last before the next batch of primaries. For Republican front-runner Donald Trump today, that meant hunting for votes and trying to win over party big-wigs.

John Yang has our report.

JOHN YANG:

Donald Trump's campaign proceeded on two fronts. The candidate stumped in Delaware.

DONALD TRUMP (R), Republican Presidential Candidate: My family asked me, dad, why are you doing this? I would rather not do it. I wish we had somebody that was so good. I don't care if it's a Republican or a Democrat. I couldn't care less.

JOHN YANG:

In Florida, a top campaign official tried to ease the concerns of members of the Republican National Committee. Senior adviser Paul Manafort described the candidate almost as an actor playing a role.

The New York Times obtained a recording of his remarks.

PAUL MANAFORT, Convention Manager, Trump Campaign:

And that's what's important, from our standpoint, for you to understand that he gets it, and that the part he's been playing is evolving into the part that now that you have been expecting that he wasn't ready for, because he had first to complete the first phase. The negatives will come down. The image is going to change.

JOHN YANG:

Ted Cruz pounced on those comments. Campaigning in Williamsport, Pennsylvania, today, he branded Trump and his team as liars.

SEN. TED CRUZ (R-TX), Republican Presidential Candidate: Yesterday, they were down in Florida meeting with party leaders, and they were saying — these are their words — that all of this is just a show, that he doesn't believe anything he's saying. He's just trying to fool gullible voters, and he's not going to do any of it, he's not going to build a wall, he's not going to deport anyone. He is telling us he's lying to us.

JOHN YANG:

In the Democratic race, Bernie Sanders is celebrating praise from Vice President Joe Biden. While not making an endorsement, Mr. Biden told The New York Times he preferred Sanders' approach.

He said:

"I like the idea of saying, we can do much more, because we can."

Today, Sanders held a town hall in Gettysburg, Pennsylvania.

SEN. BERNIE SANDERS (VT-I), Democratic Presidential Candidate: My hope is there will be a record-breaking turnout on Tuesday.

(CHEERING AND APPLAUSE)

JOHN YANG:

Clinton also campaigned in Pennsylvania, focusing on pay equity, citing the decision to put a woman on the $20 bill.

HILLARY CLINTON (D), Democratic Presidential Candidate: I'm very excited about Harriet Tubman and the other women who are going to be included on our money. But I also want to make sure that women are making the money.

JOHN YANG:

Pennsylvania is the biggest prize among the five states that vote on Tuesday.

For the "PBS NewsHour," I'm John Yang.

JUDY WOODRUFF:

In London today, President Obama called for overturning North Carolina's new law on public bathrooms. It limits transgender people to the facility that corresponds to their sex at birth.

Mr. Obama said the law is wrong, but he emphasized that Britons are welcome to visit. The British government has issued a travel advisory warning of possible discrimination in some U.S. states.

The president also weighed in one Britain's upcoming vote on whether to leave the European Union. He penned an op-ed article in The Daily Telegraph, writing — quote — "The U.S. and the world need your outsized influence to continue, including within Europe."

Later, he followed up on his appeal at a news conference with Prime Minister David Cameron.

PRESIDENT BARACK OBAMA:

Part of our special relationship, part of being friends it is to be honest and to let you know what I think.

And, speaking honestly, the outcome of that decision is a matter of deep interest to the United States, because it affects our prospects as well. The United States wants a strong United Kingdom as a partner, and the United Kingdom is at its best when it's helping to lead a strong Europe.

JUDY WOODRUFF:

The president also warned that the U.S. would be in no hurry to write a free trade deal with Britain if it does exit the E.U.

But the candor wasn't appreciated by some, including London Mayor Boris Johnson, who heads the Leave campaign.

MAYOR BORIS JOHNSON, London:

It's something to which the Americans would never submit their own democracy. America is a proud democracy, built on principles of liberty, the idea of the sanctity of representation and no taxation without representation. It is very odd. It is perverse. It is hypocritical.

JUDY WOODRUFF:

Johnson also blasted the president's decision to move a bust of Winston Churchill from the Oval Office. He called it — quote — "a symbol of the part-Kenyan president's ancestral dislike of the British empire."

President Obama didn't respond directly to the jibe, but he did say that he moved the Churchill bust to his private study after he had a bust of Martin Luther King Jr. placed in the Oval Office.

The United States announced today that it's buying roughly 35 tons of so-called heavy water from Iran. The liquid is used to make weapons-grade plutonium, and last year's nuclear deal calls for Iran to sell its excess stockpile. Republican leaders in Congress today criticized the purchase as a dangerous precedent.

The number of migrants arriving in Greece is rising again. The International Organization for Migration says more than 150 people reached the Greek islands from Turkey on each of the last three days. Initially, a European Union deal with Turkey had cut arrivals to near zero.

Back in this country, medical officials completed an autopsy on Prince, but said it could take weeks to fix the cause of death. The pop music great was found dead yesterday at his home in suburban Minneapolis.

Today, as an impromptu memorial swelled with balloons and flowers, investigators said some points are already clear.

JIM OLSON, Carver County, Minnesota, Sheriff:

There were no obvious signs of trauma on the body at all.

We have no reason to believe at this point that this was a suicide, but, again, this early on in this investigation and it's continuing to — we will continue to investigate.

JUDY WOODRUFF:

The sheriff and the medical examiner's office wouldn't confirm or deny reports that Prince might have overdosed on painkillers last week.

Wall Street ended the week with a lackluster day. The Dow Jones industrial average gained 21 points to close at 18003. But the Nasdaq fell 39, and the S&P 500 added just a fraction. For the week, the Dow and the Nasdaq gained half-a-percent. The S&P lost more than half-a-percent.

And thousands of people have gathered in Boston this weekend for PAX East, one of the world's leading gaming festivals. Organizers say it's like Woodstock for gamers, where serious players can compete and preview what's new. The buzz this year is all about virtual reality games that use headsets to transport users to alternate worlds.

Still to come on the "NewsHour": an alarming rise in suicide rates, including among teenage girls; Virginia's governor explains why 200,000 felons can now vote in November; Mark Shields and David Brooks analyze the week's news; fighting the terror group Al-Shabaab in a propaganda war; and much more.